Traditionally plant residues such as leaves, areca palm sheaths have been used in India as raw material for forming different articles such as plates, cups, saucers etc. for serving food. These articles are hitherto prepared by various methods. A few of the very commonly used methods are explained below.
Normally, plates are formed by stitching the leaves/sheaths into desired shape. More commonly, plates are formed by stapling several leaves together using split plant stems pins. Leaves such as that of Butea or Bauhunia plant are washed and softened and placed on a flat surface and depending on the plate size desired, two or more of the leaves are stitched together at the edges, or stapled using small sharp pins made of twigs or coconut ribs manually. The stitched plates are then dried in shade and are used as leaf plates.
For making small cups the leaves of Butea, Bauhunia or any other leaves such as Banana or sheaths of areca palm, are washed, softened and folded to form the desired shape. The folding provides the dimple or shape of a cup, and the folds are fixed by stitching or by stapling using pins made of plant twigs or coconut leaf ribs manually. The folded stitched cups are dried to retain the shape and rigidity.
The articles made from leaves and sheaths according to the methods explained above have enjoyed the advantage of being biodegradable and eco-friendly. Cups and saucers of this nature have been traditionally used for vending of butter and other semi-solid materials.
However, such articles have the disadvantage of being held together with plant stem pins, stitching, leaves, crevices leading to harboring of micro organisms, due to conditions under which they are prepared, poor physical strength and irregular dimensions and lack of elegance.
The Applicants have previously developed a manually operated bio-plate casting machine. The device is shown in FIG. 1 is being currently used.
The device has a main frame (g), movable die (a) and a stationary punch (b). Electric coils (c), heats the punch for thermosetting of the bio-plates. A thermostat (d) not shown in the figure controls the temperature of the punch to the preset temperature. The untrimmed plant leaf is kept in between the jaws of punch and the die and force is applied manually. The toggle mechanism (e) transmits the load to the movable die and to the plant leaf. The person operating the machine stands at the end of the toggle (f) for the application of the force. Trimming of the plates and cups to its final shape is done manually. A panel board (h) is provided for housing all the electricals. The time of heat treatment depends on the thickness of the plant leaf and the moisture content and the same is controlled manually. The production capacity of this machine is around 120 nos./h. The machine is labor intensive and the quality of casting depends on the skill of the operator.
Applicants co-pending Indian patent application no. 2305/Del/95 dated Dec. 13, 1995 also provides a bio-plate casting machine. FIG. 2 of the accompanying drawings show the device described in the Applicants co-pending Indian Patent Application No. 2305/Del/95.The device comprises of a die-set (1), press cylinder (2), ejection cylinder (3), discharge cylinder (4), ejector (5) heating coil (6), photo sensor (7), the main frame (8), pneumatic solenoid valves (9), air hoses (10), timers (11), counter (12), temperature controller (13), a control panel (14), air compressor (15) and anti-vibration mounts (16).
The device comprises of: a frame (8) to which a die set (1) is fixed, the die set (1) comprises of a punch (1a) and a die (1b), a gap is provides between the punch and the die for feeding the plant leaf material to be shaped. A plurality of solenoid valves (9) and a discharge cylinder (4) being fixed to the sides of the main frame (8), the discharge cylinder (4) being fixed above the solenoid valves (9), the ejector (5) being housed inside the die set (1), and being connected to an ejector cylinder (3) for facilitating the vertical movement of the ejector (5), the punch (1a) connected to a press cylinder (2) for providing vertical movement to the punch (1a), the punch (1a) housing the heating coil (6) and provided at its bottom a cutting edge in the die (1b) housing a photo sensor (7) for actuating the solenoid valves (9), the control panel (14) comprising of a temperature controller (13) the output of which being connected to the input of a heating coil (6) and the electric current for heating the coil being supplied through this output, the output of the heating coil (6) being connected to the thermocouple of the temperature controller (13), to sense the timer of the punch (1a) and the dieset (1), at least three electronic timers (11), the input of the first electronic timer being connected in parallel to the other timer, the electric current to this timer being applied through the input of the said timer, the output of the last timer being connected to the respective solenoid valves (9), the output of the photosensor being connected to the first timer and one of the outputs of the first timer being connected to a counter, the control panel (14) being mounted on the main frame (8). The device of our copending patent application no. 2305/DEL/95 dated Dec. 13, 1995, has the following drawbacks.    1. The operation is not continuous.    2. Handling of the raw leaf is difficult.    3. The heating time of the die is more.    4. The gap between the die set cannot be adjusted.    5. The die and punch set is not interchangeable.    6. The operating pressure of the main pneumatic cylinder is high.    7. The material handling is labor intensive.    8. The production capacity of the machine is low.    9. The machine cannot be moved from place to place.    10. The machine vibrates during the operation.    11. Productivity is low.    12. The operation and maintenance is expensive.
Thus, there is a need to provide an improved device that overcomes the aforesaid drawbacks and provides features such as continuous production of bio-plates, high productivity, less hardship for manual labor, less vibration, interchangeable die set and a provision to adjust the gap between the punch and the die.